Abstract:Performance assessment(PA) is the application of risk assessment in the field of nuclear waste geological disposal. PA was initially adopted as a measure to quantitatively demonstrate the performance of both natural and engineered barriers of a repository,which eventually leads to building a safety case. The ultimate guidelines for PA are the principles and standards that are recognized and accepted by international communities. In practice,PA virtually links major parts of a repository program including waste characterization,disposal concept,site selection and characterization. This places PA in the unique position of the nuclear waste management program:PA can be used as a decision-making tool to aid repository program planning and management in order to meet the programmatic goals cost effectively. The article introduces PA from the top-down viewpoint and covers topics of methodology,modeling,and uncertainty. Finally,the authors provide some specific suggestions to Chinese scientists.